Redistribution of iron oxides in aggregates induced by pe+pH variation alters Cd availability in paddy soils
Redistribution of iron oxides in aggregates induced by pe+pH variation alters Cd availability in paddy soils
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pe pH 变化引起的团聚体中铁氧化物的重新分布改变了稻田土壤中镉的有效性
DOI：
10.1016/j.scitotenv.2020.142164
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Han Yun
中科院分区：
文献类型：
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作者：
Li Shanshan;Chen Shibao;Wang Meng;Lei Xiaoqin;Zheng Han;Sun Xiaoyi;Wang Lifu;Han Yun
在本研究中，探讨了不稳定的 pe + pH 水平对不同大小土壤部分中 Fe 氧化物转化的影响及其对 Cd 形态的影响。从中国两个地点采集的稻田土壤样品在四种 pe + pH 条件之一下培养两个月：淹水 + N2(T1)、淹水 (T2)、70% 持水量 (T3) 和 70% 持水量 + O2(T4)。采用化学分析和 X 射线衍射 (XRD) 来鉴定水稻土中 Fe 和 Cd 的矿物相和形态。结果表明，土壤 pe + pH 水平的降低有利于赤铁矿和针铁矿等结晶良好的铁氧化物 (Fec) 转化为结晶不良 (Feo) 和有机复合物 (Fep) 形式。这种转化促进了 Cd 与 Fe 氧化物的结合，是土壤 DTPA（二乙烯三胺五乙酸）可提取 Cd 含量降低 41.8% 的主要原因。此外，pe+pH值的下降使两种淹水处理的土壤颗粒部分中的铁浓度降低了0.2-2毫米（17.8%-30.6%）和<0.002毫米（20.7%-31.7%）。 Fe 浓度的降低与这些相同部分中较少的 Fec 含量以及更多的 Feo 和 Fepin 粗聚集体密切相关 (P<0.01)。重要的是，0.002–2 mm 级分中 Feo 和 Fepin 含量的增加与较大粒径级分中 Fe-/Mn-氧化物结合的 Cd (OX-Cd) 含量显着相关 (P<0.01)。此外，OX-Cd含量的增加对于降低DTPA-Cd含量起到了至关重要的作用。这项研究表明，低 pe + pH 值有利于结晶 Fe 氧化物转化为结晶不良的有机络合相，从而促进 Cd 在粗团聚体中的积累，并增强稻田土壤中 Cd 的稳定性。
In this study, the effect of unstable pe + pH levels on the transformation of Fe oxides in different-sized soil fractions and its impact on Cd speciation were explored. Paddy soil samples collected from two locations in China were cultivated for two months under one of four pe + pH conditions: flooding + N2(T1), flooding (T2), 70% water holding capacity (T3), and 70% water holding capacity + O2(T4). Chemical analysis and X-ray diffraction (XRD) were used to identify the mineralogical phases and species of Fe and Cd in paddy soils. The results show that the decrease of soil pe + pH level favored the transformation of well-crystallized Fe oxides (Fec), such as hematite and goethite, into poorly-crystallized (Feo) and organically-complexed (Fep) forms. The transformation promoted the binding of Cd to Fe oxides and was primarily responsible for up to a 41.8% decrease of soil DTPA (diethylenetriaminepentaacetic acid)-extractable-Cd content. In addition, the decline in pe + pH value reduced Fe concentrations in soil particle fractions of 0.2–2-mm (17.8%–30.6%) and <0.002-mm (20.7%–31.7%) of the two flooding treatments. The decreased Fe concentrations were closely associated with less Feccontents in these same fractions and more Feoand Fepin coarser aggregates (P<0.01). Importantly, the increase in contents of Feoand Fepin the 0.002–2 mm fraction were significantly correlated with content of Fe-/Mn-oxide-bound Cd (OX-Cd) in larger particle-size fractions (P<0.01). Furthermore, the increasing content of OX-Cd played a crucial role in reducing DTPA-Cd content. This study demonstrates that low pe + pH values favor the transformation of crystalline Fe oxides into a poorly-crystallized and organically-complexed phase, which facilitates Cd accumulation in coarser aggregates and enhances Cd stability in paddy soils.